Biomechanical seat construction

ABSTRACT

A biomechanical seat construction ( 1 ) comprising a seat ( 2 ) and a back rest ( 3 ) with adjustable support ( 4 ) of the pelvis, the seat comprising a front seat part ( 5 ) and a rear seat part ( 6 ), and means ( 8 ) for displacement of the front seat part ( 5 ) and the rear seat part( 6 ) vertically relatively to each other. In a first position the seat surface ( 5   a ) of the front seat part ( 5   a ) is generally positioned at a level which is essentially higher that the seat surface ( 6   a ) of the rear seat part ( 6 ) when both seat surfaces ( 5   a,   6   a ) are generally horizontal. Means is provided for displacement of the front seat part ( 5 ) and the back seat part ( 6 ) vertically relatively to each other to at least a second position. Said means comprise at least one arm ( 8 ) for supporting the rear seat part( 6 ). In said second position the seat surface ( 6   a ) of the rear seat part ( 6 ) has an angle relatively to a horizontal plane. The displacement of the rear seat part ( 6 ) between the first and the second positions are made in the form of a curved movement in such a way that the front edge ( 6   b ) of the rear seat part ( 6 ) moves vertically relatively to the seat surface ( 5   a ) of the front seat part ( 5 ).

FIELD OF THE INVENTION

The invention relates to a biomechanical seat construction according to the preamble of claim 1.

BACKGROUND OF THE INVENTION

EP 0 957 721 B1 describes a chair comprising a seat and a back rest, the seat comprising a front seat part and a rear seat part separated by a boundary. As seen in a horizontal plain the boundary between the front and rear seat parts is generally perpendicular to the longitudinal direction of the seat portion of the chair. The chair is provided with means for enabling vertical displacement of the rear seat part obliquely downwards and backwards while maintaining the same horizontal direction of both seat parts.

By the above-mentioned chair construction it is achieved that the rear edge of the front seat part generally is positioned about a vertical plan through the hip joints of the user, whereby the bottom/hip part is substantially relived from pressure, and will in fact be hanging behind the rear, preferably concave, edge of the front seat part.

U.S. Pat. No. 7,322,651 B1 describes a chair comprising at least one seat and a back rest, the seat comprising a front seat part and a rear seat part which are separated by boundary. In one embodiment the back seat part is arranged at the same level as the front seat part and may be tilted downwardly relatively on the front seat part while maintaining the front edge of the rear seat part at essentially the same level as the back edge of the front seat part. In another embodiment the rear seat part is placed in a parallel motion in vertical direction relatively to the front seat part while maintaining the same horizontal direction of both seat parts.

The chair constructions described in the above-identified documents permits that the back rest of the chair steady the lumber region of the use, and the friction between the back rest and the back of the user contributes to support the upper body the user. When the vertical through the gravity of the upper body of the user extends close to the back edge of the front seat part of the seat the weight of the user will exert a small torque around the back edge. The user may therefore in an easy way by his own muscular strength keep the bottom/hip portion at a reduced load against the rear seat part, the weight of the user being distributed in a favourable way also to the underside of the thighs against the seat surface of the front seat part. This results in that the loin part of the user is relieved and that the user in a simple way can give the loin part a curving in the median plane which minimizes back pains and minimizes the risk of appearance of back pains, respectively, of a user sitting down.

It has now turned out that the above-mentioned chair constructions are not optimal regarding relief of the pelvis/loin part, and particularly not regarding maintaining the natural S-curve of the back.

SUMMARY OF THE INVENTION

One object of the biomechanical seat construction according to the invention is to give essentially healthy people the possibility to obtain a seating position which relives the back and pelvis of the user and gives the possibility to, where appropriate, reduce back pains which otherwise will arise when sitting down, or prevent that back pains occur when sitting down.

A further object of the present biomechanical seat construction is to further improve the seat comfort of the user while maintaining the natural S-curve of the back.

Yet a further object is to achieve a relief function of the back and/or the pelvis already in the original position of the chair.

These objects are achieved according to the invention by a biomechanical seat construction comprising a seat and a back rest with adjustable support of the pelvis, the seat comprising a front seat part and a rear seat part separated from each other by a boundary, which as seen in an horizontal plane is generally curved in the cross direction of the seat of the chair, means for displacement of the front seat part and the rear seat part vertically relatively to each other, each of the seat parts has a seat surface having a front edge and a rear edge and side edges, wherein in a first position the seat surface of the front seat part is generally positioned at a level which is essentially higher that the seat surface of the rear seat part when both seat surfaces are generally horizontal, means being provided for displacement of the front seat part and the back seat part vertically relatively to each other to at least a second position, said means comprise at least one arm for supporting the rear seat part, said at least one arm being pivotally attached to a frame for supporting at least the front seat part and the rear seat part, wherein in said second position the seat surface of the rear seat part has an angle relatively to the horizontal plane, and wherein the displacement of the rear seat part between the first and the second positions are made in the form of a curved movement in such a way that the front edge of the rear seat part moves vertically relatively to the seat surface of the front seat part.

Preferred embodiments of the invention are defined in the dependent claims.

SHORT DESCRIPTION OF THE DRAWINGS

The invention will be described more closely below with reference to the attached drawings, on which

FIG. 1 is a schematically side view of a biomechanical seat construction according to the invention, and

FIG. 2 is the same view as in FIG. 1 with the rear seat part shown in different positions and with a front end of a front seat part connected to a frame.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the below description the longitudinal direction of front and rear seat part is defined as the direction seen the longitudinal direction of the seat of the biomechanical seat construction, and correspondingly the cross direction of front and rear seat part is defined as the direction seen the cross direction of the seat of the biomechanical seat construction.

FIG. 1 shows a schematic side view of a biomechanical seat construction 1. By biomechanical seat construction is meant, but not limited to, chairs, armed chairs, and apparatus for stretching the back etc. The biomechanical seat construction 1 shown in FIG. 1 is shown without any underbody, since this can be constructed in different ways and does not form a part of the invention. The biomechanical seat construction 1 comprises a seat 2, a back rest 3 with arm rests 3 a and adjustable pelvis support 4. The seat 2 comprises a front seat part 5 and the rear seat part 6, which are separated from each other by a boundary 7, which when viewed in a horizontal plane is generally curved in cross direction of seat the chair.

Moreover, it comprises means, not shown, for displacement of the front seat part 5 and the back seat part 6 on one hand vertically and on the other hand horizontally relatively to each other. The respective seat parts 5, 6 has each a seat surface 5 a, 6 a with a front and rear edge 5 b, 5 c, 6 b, 6 c and side edges 5 d, 6 d, of which only one, the right, is shown on the drawings.

FIG. 1 shows a first position, normal position, of the seat surface 5 a of the front seat part 5 generally positioned in a plane which is substantially higher than the plane of the seat surface 6 a of the rear seat part 6 when both seat surfaces 5 a, 6 a are generally horizontal.

FIG. 2 shows a second position of the rear seat part 6. In this second position the rear seat part 6 can be raised as shown by solid lines or can be lowered as shown by broken lines i.e. in the second position the seat surface 6 a of the rear seat portion 6 has an angle relatively to the horizontal plane. Although the seat support is shown schematically attached to a frame 9 by a bent bracket 10, for instance, it should be understood that the rear seat part 6 can be lowered without interfering with the bent bracket or that the bent bracket prevent the pelvis of a person sitting on the biomechanical seat construction from being supported by the seat surface 6 a in the different positions that the seat surface can obtain. The front and rear seat portions 5, 6 are either being made of a suitable material which in it self can take the load of a person sitting down or maybe provided with a load bearing construction.

The means for displacement of the rear seat part 6, vertically relatively to the front seat part 5 is formed by at least one arm 8, for instance, supporting the rear seat 6 and pivotably attached to the frame 9, which carries said at least the two seat ports 5, 6. The back rest 3 is supported by the bent bracket 10. The pivotable attachment of said at least one arm 8 is preferably done by an axle 11. This axle 11, besides being pivotably attached to the frame 9, is also displaceably arranged in the horizontal plane in the longitudinal directions of the seat of the chair by suitable means, not shown, for instance in the form of an elongated opening arranged in the frame 9 having seats for achieving distinct adjustment positions in generally the horizontal plane of the axle, or the axle may be continuously adjustable in said horizontal plane. The pivotal position of the axle 11 and thereby the position of the seat surface 6 a of the rear part of the seat part 6 may preferably be continuously adjustable within wide limits. By the pivotable arm 8 the rear seat portion 6 describes a curved movement at its adjustment between the first and the second positions. Moreover, the axle 11 is positioned in front of the boundary 7 of the rear edge 5 c of the seat surface 5 a of the front seat part 5 and at distance from a lower surface 12 of the front seat part 5 for enabling movement of the seat surface 6 a of the rear seat part 6 vertically above and below, respectively, a generally horizontal plane aligned with the seat surface 5 a of the front seat part 5. By placing the fulcrum of the arm 8 (axle 11) in this way an effective displacement backwardly of the pelvis is achieved, which is not obtained by the chair construction described in U.S. Pat. No. 7,322,651 B1, for instance, in which the fulcrum of the rear seat part to the front seat part is so located at the front edge of the seat surface of rear seat part, during the whole pivoting motion of the rear seat part, is located at the same level as the seat surface of the front seat part. The pivotable attachment of said at least one arm 8 to the frame 9 is located at a distance L from the rear edge 5 c of the seat surface 5 a of the front seat part 5 and amounts to between 0.1 L and 0.9 L, preferably 0.3 L and 0.6 L in which L is defined as the length of the front seat part 5 in the longitudinal direction of the seat of the chair. Furthermore, the rear seat part 6 is in it self or in combination with the front seat part 5 displaceablely arranged forwardly in the longitudinal direction of the seat of the chair from a back seated location of a rear edge 6 c of the rear seat part 6, relatively to a vertical line A of a sway-back support 4 arranged at the back rest 3 by minus 10 to 40 cm, preferably 0 to 30 cm relatively this vertical line A. The back rest 3 with associated sway-back support 4 is thereby designed to allow that the arched movement of the rear seat part 6 could be made without any interference. The width of the boundary 7, i.e. the distance between the rear edge 5 c of the front seat part 5 and the front edge 6 a of the rear seat part 6, should be sufficiently large to allow for a pivoting motion upwardly of the rear seat part relatively to the front seat part.

As can be seen in FIG. 1 and FIG. 2 the seat surface 5 a of the front seat part 5 is preferably provided at either its front or rear edge or both 5 b, 5 c with a bevelling having an angle relatively to the horizontal plane. Furthermore, the edge 5 c of the seat surface 5 a should be flexible resilient, and preferably also the corresponding load carrying portion of the front seat part 5 should be flexible resilient and possibly bevelled. This for achieving a soft transition at said edge to prevent locally high stresses against the underside of the user's thighs.

The front seat part 5 may, as shown in FIG. 1, be attached to the frame 9 by at least one elastically yieldable means 13, for instance made of rubber. This results in that the front seat part is not locked in any degree of freedom.

As can be seen from FIG. 2 the front seat part 5 may be connected to the frame 9 by on one hand the elastically yieldable means 13 and on the other hand by one or several means 14 a, 14 b, 14 c for pivotable fixation of the front seat part 5 in the longitudinal direction of the seat of the chair, for instance in the form of pivoting axles 14 a, 14 b and 14 c. When the front seat part 5 is connected to the frame by on one hand the elastically yieldable means 13 and on the other hand the pivoting axle 14 c the rear portion of the front seat part 5 will be elastically resilient in a vertical direction, and in the same way the front portion of the front seat part 5 will be elastically resilient in a vertical direction, when the front seat part is connected to the frame by on one hand the elastically yieldable means 13 and on the other hand the pivoting axle 14 a. Also the rear seat part 6 can be connected to the arm 8 by elastically yieldable means (not shown).

In an embodiment not shown may either the seat surface 5 a of the front seat part 5 or seat surface 6 a of the back seat part 6, or both 5 a, 6 a, be divided into at least two portions, and said portions may be adjustable independently of each other. The seat surface of the rear seat part 6 may be flat, resilient or convexly shaped, i.e. may be bowl-shaped. In an other embodiment not shown the seat surface 5 a of the front seat part 5 may in the longitudinal direction of the seat of the chair be essentially convexly shaped and in the cross direction of the seat of the chair essentially concavely shaped. Moreover, the front seat part 5 may at its front edge 5 b be elastically attached to the frame, as shown in FIG. 1, or alternatively the seat surface 5 a of the front seat part 5 may at its front edge 5 b be elastic. Even though the front seat part 5 is shown having a general horizontal seat surface 5 a it is obvious for a man skilled in the art that this seat surface may be angled in suitable way. Furthermore, in a known manner the seat is adjustable to the weight of a person so as to offer good comfort, and the back rest is displaceably arranged in the longitudinal direction of the seat of the chair.

In a further embodiment not shown a belt may be attached at a suitable height of the back rest 3. The belt is adapted to be tightened around the chest of the user for fixation of the back of the user against the back rest and to further increase the relief of the back, the loin and the pelvis. By raising the rear seat portion, when the user is fastened to the back rest by the belt is also possible to instead compress the back, the loin and the pelvis. 

1. A biomechanical seat construction comprising a seat and a back rest with adjustable support of the pelvis, the seat comprising a front seat part and a rear seat part, separated from each other by a boundary, which as seen in an horizontal plane is generally curved in the cross direction of the seat of the chair, means for displacement of the front seat part and the rear seat part vertically relatively to each other, each of the seat parts has a seat surface having a front edge and a rear edge and side edges, wherein in a first position the seat surface of the front seat part is generally positioned at a level which is essentially higher that the seat surface of the rear seat part when both seat surfaces are generally horizontal, means being provided for displacement of the front seat part and the back seat part vertically relatively to each other to at least a second position, said means comprise at least one arm for supporting the rear seat part, said at least one arm being pivotally attached to a frame for supporting at least the front seat part and the rear seat part via said arm, wherein in said second position the seat surface of the rear seat part has an angle relatively to a horizontal plane, and wherein the displacement of the rear seat part between the first and the second positions are made in the form of a curved movement in such a way that the front edge of the rear seat part moves vertically relatively to the seat surface of the front seat part.
 2. Biomechanical seat construction according to claim 1, wherein the pivotable attachment of said at least one arm to the frame is situated in front of the boundary of the rear edge of the seat surface of the front seat part and at a distance from a lower surface of the front seat part so as to allow displacement of the seat surface of the rear seat part vertically above and below, respectively, the seat surface of the rear seat part.
 3. Biomechanical seat construction according to claim 2, wherein the pivotable attachment of said at least one arm to the frame is located at a distance (L) from the rear edge of the seat surface of the front seat part amounting to between 0.1 L and 0.9 L, preferably 0.3 L and 0.6 L, L being defined as the length of the front seat part in the longitudinal direction of the seat of the chair.
 4. Biomechanical seat construction according to claim 1, wherein the seat surface of the front seat part is at its rear edge bevelled in an angle relatively the horizontal plane.
 5. Biomechanical seat construction according to claim 1, wherein the seat surface of the front seat part has in its longitudinal direction a general convex shape and in its cross direction a generally concave shape, and wherein the rear portion of the seat portion of the seat part is bowl-shaped.
 6. Biomechanical seat construction according to claim 1, wherein the front seat part is at its front edge elastically attached to frame.
 7. Biomechanical seat construction according to claim 1, wherein the seat surface of the front seat part is at its front edge resilient.
 8. Biomechanical seat construction according to claim 1, wherein the pivotable attachment of said at least one arm to the frame is displaceably arranged in essentially a horizontal plane of the longitudinal direction of the seat of the chair.
 9. Biomechanical seat construction according to claim 1, wherein either the seat surface of the front seat part or seat surface of the rear seat part or both are divided into at least two portions, and wherein said portions are adjustable independently of each other.
 10. Biomechanical seat construction according to claim 1, wherein the front seat part is connected to the frame by at least one elastically yieldable means.
 11. Biomechanical seat construction according to claim 1, wherein the rear seat part is displaceably arranged forwardly in the longitudinal direction of the seat of the chair from a rearmost position relatively a vertical line (A) of a sway-back support arranged at the back rest as seen from the rear edge of the rear seat part, by minus 10 to 40 cm, preferably 0 to 30 cm relatively this vertical line (A). 